I tried a Stop & Go on a puncture today, it didn't work, but this is more to do with the type of puncture I got. A 2" (50mm) screw had gone in at an angle to the centre of the tread, and I'm guessing it had left an elongated hole on the inner surface of the tyre which the mushroom head couldn't seal, so I may need a new back tyre, shame as it's only half worn.